// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_WM_CORE_FOCUS_RULES_H_
#define UI_WM_CORE_FOCUS_RULES_H_

#include "ui/wm/wm_export.h"

namespace aura {
class Window;
}

namespace wm {

// Implemented by an object that establishes the rules about what can be
// focused or activated.
class WM_EXPORT FocusRules {
public:
    virtual ~FocusRules() { }

    // Returns true if |window| is a toplevel window. Whether or not a window
    // is considered toplevel is determined by a similar set of rules that
    // govern activation and focus. Not all toplevel windows are activatable,
    // call CanActivateWindow() to determine if a window can be activated.
    virtual bool IsToplevelWindow(aura::Window* window) const = 0;
    // Returns true if |window| can be activated or focused.
    virtual bool CanActivateWindow(aura::Window* window) const = 0;
    // For CanFocusWindow(), NULL is supported, because NULL is a valid focusable
    // window (in the case of clearing focus).
    virtual bool CanFocusWindow(aura::Window* window) const = 0;

    // Returns the toplevel window containing |window|. Not all toplevel windows
    // are activatable, call GetActivatableWindow() instead to return the
    // activatable window, which might be in a different hierarchy.
    // Will return NULL if |window| is not contained by a window considered to be
    // a toplevel window.
    virtual aura::Window* GetToplevelWindow(aura::Window* window) const = 0;
    // Returns the activatable or focusable window given an attempt to activate or
    // focus |window|. Some possible scenarios (not intended to be exhaustive):
    // - |window| is a child of a non-focusable window and so focus must be set
    //   according to rules defined by the delegate, e.g. to a parent.
    // - |window| is an activatable window that is the transient parent of a modal
    //   window, so attempts to activate |window| should result in the modal
    //   transient being activated instead.
    // These methods may return NULL if they are unable to find an activatable
    // or focusable window given |window|.
    virtual aura::Window* GetActivatableWindow(aura::Window* window) const = 0;
    virtual aura::Window* GetFocusableWindow(aura::Window* window) const = 0;

    // Returns the next window to activate in the event that |ignore| is no longer
    // activatable. This function is called when something is happening to
    // |ignore| that means it can no longer have focus or activation, including
    // but not limited to:
    // - it or its parent hierarchy is being hidden, or removed from the
    //   RootWindow.
    // - it is being destroyed.
    // - it is being explicitly deactivated.
    // |ignore| cannot be NULL.
    virtual aura::Window* GetNextActivatableWindow(
        aura::Window* ignore) const = 0;
};

} // namespace wm

#endif // UI_WM_CORE_FOCUS_RULES_H_
